Catalytic oxidation of benzene



UNITED STATES PATENT OFFICE.

JOHN M. WEISS, OF NEW YORK, N. Y., AND CHARLES R. DOWNS, OF OLIFFSIDE, NEW JERSEY, ASSIGNORS TO THE BARRETT COMPANY, A CORPORATION OF- NEW JERSEY.

CATALYTIC OXIDATION OI BENZENE.

No Drawing.

To all whom it may coiwern:

Be itknown that we, (-1).JonN M. Wmss and (2) CHARLES R. DOWNS, citizens of the United States, residing at (1) 210 West 110th street and (2) Clifl'side, in the counties of (1) New York and(2) Bergen and States of (1) New York and (2) New Jersey, have invented certain new and useful Improvements in Catalytic Oxidation of Benzene, of which the following is a specification.

This invention relates to the catalytic oxidation of benzene and to the production of )roducts of partial oxidation therefrom; and it comprises a method of effecting the partial'or selective oxidation of benzene by subjecting the benzene to oxidation, by oxy- Bpeolfloation of Letters Patent.

gen either alone or admixed with other gases, or by means of an oxygen containing gas in the presence of a catalyzer.

The invention is based upon the discovery that by subjecting benzene (benzol 0 H to oxidation, in the presence of an appropriate catalyzer, and at an appropriate temperature, the benzene ring or nucleus may be broken and a selective or partial oxidalion thereof takes place with the formation 'of products of partial oxidation, some of these products being of the aliphatic or straight chain series.

It is, of course, well known that benzene may be oxidized by combustion, much the same as other combustible hydrocarbons, with the formation of carbon dioxid and water. It is commonly considered, however, that benzene resists oxidation by air (oxygen) as distinguished from combustion even when mixtures of benzene and air are subjected to the influence of ultra-violet light. Accordingly, we regard our discovery as 40 -one involving a new reaction of benzene,

atoms of the benzene ring or nucleus.

namely, the selective or partial oxidation of the benzene, with disruption or breaking of the benzene ring or nucleus, and resulting formation of straight chain or aliphatic compounds.

We have also found that, by appropriate regulation of the conditions of the catalytic oxidation, the benzene ring or nucleus can be broken or disrupted in a particular manner, with the formation of straight chain derivatives containing four of the carbon We have further found that oxidation of the benzene ring, under appropriate conditions, will result in the formation of formalde- Patented Oct. 14, 1919.

\ Application med April 8, 1919. Serial No. 288,458.

' hyde.

The catalytic oxidation can moreover he so carried out that both formaldehyde and four carbon atom derivatives, such as malelc acid, are obtained at the same time or during the-course of the. sauie reaction. Qarbon dioxid and water are, at the same time, formed to a certain extent.

linden certain conditions of reaction, WlllCll Wlll be referred to below, a smaller degree of oxidation of a portion of the benzene will take place so that the benzene mug is not split but is oxidized directly to produce qulnone in which two of the hydrogen atoms In the ara position in the benzene ring are replace by two oxygen atoms.

Theinvention will be further described in connection with the following specific example, illustrative thereof, but it will be understood that we do not limit ourselves to the details of this example, and that we regard the invention as of a more comprehennated with vanadium oxid which is heated to a temperature around 300 C. or somewhat the-rea'bove, or more generally, between 300 C. and around 550 C. The proportions of oxygen (in the form of air) and benzene can be varied, but may be as low as one molecular weight of oxygen to two molecular weights of benzene (32 parts of oxygen to 156 parts of benzene by weight). Increasing the proportion of oxygen (air) will cause a corresponding increase in the oxidizing effect. Theoretical considerations point to the proportions of seven atomic weights.of oxygen to one molecular weight of benzene as the optimum proportions when the reaction follows the course of the second equation given below.

The vanadium oxid does not appear to enter into the reaction, but seems rather to function as an oxygen carrier or catalyzer, which, by itspresence, causes the reaction between the oxygen and benzene to take place, with resulting selective or fractional oxidation of the benzene'under the influence same operation, quinone, maleic acid, formaldehyde, carbon dioxid, and water. Formaldehyde is not formed to the extent which theoretical considerations would indicate. The actual proportion thereof varies with conditions of operations. and' sults obtained.

on on l H10 on 0/ on o COOH H on cH 30 I on on o 10 n c eo2 on on on 11 Q coon on f. on i on Where a considerable excess of benzene is used over and above that which is oxidized, the remaining benzene will in part pass through practically unchanged, and the reaction gases Will be correspondingly diluted by the excess benzene present during the reaction. The nitrogen of the air will have a corresponding diluent efi'ect. Any steam if present, will similarly have a diluent effect, for example, in case moist air, instead of dry air, is used in the process of the above specific example. Since water is practically always formed as a product some steam is resent as a consequence.

The di ution with nitrogen or other diluent, and also a variation of the time of contact with the catalyst, as well as a change of the temperature between the specified limits above mentioned or a change in the relative proportion of benzene and oxygen, will each cause a change in the amounts and relative proportions of the products produced. It has been found that at atmospheric pressure when passing equal weights of benezene vapor and air in contact with vanadium oxid as a catalyst at such velocity that the mixture stays in contact with the catalyst about '1" of a second a maximum amount of maleic acid is obtained with catalyst temperatures from about 400 C.

COOH

to 450 (1., although appreciable amounts are obtained at temperatures considerably outside of this range. At temperatures above the approximate maximum of about 550 C. the yield of malcic acid decreases rapidly and diphenyl is found in increasing quantities among the products of reaction as the hi her temperatures are employed.

The benzene (benzol) used should preferably be of high purity, or, if admixed with impurities, it should be substantially free from im )urities of such a character as would prejudice the desired selective and partial catalytic oxidation.

It will be evident that various types of a 'iparatus may he used for carrying out the process of the present invention and for wringing about the necessary contact of the reacting gases with the catalyst and for maintaining the proper temperature for the catalytic reaction. Accordingly, we do not deem it necessary to describe in further detail such types of apparatus.

It will be evident also that the various conditions of the reaction are capable'of variation. Among these conditions may be mentioned the temperature and pressure at which the reaction is carried out, the time of contact of the reactive gases with the catalyst, the proportion of catalyst to the reacting gases, and the relative roportions of benzene and oxygen and of di uent gases, such as nitrogen. The reaction may thus be carried out at atmospheric pressure, or at in-. creased or diminished pressures. The oxidizing effect can be modified by further dilating the reacting gases, as by returning the air, impoverished in oxygen by the reaction, to dilute the reacting gases in the further carrying out of the process, or by mixing oxygen with the air to increase the oxygen content thereof, or by using oxygen alone without other diluent,or by using oxygen in admixture with other gases than those contained in air, etc.

It will be evident also that the time of contact of the reacting gases with the catalyst can be varied by increasing the catalytic mass or by decreasing the speed at which the reacting gases pass through or in contact with the catalyst. These and like variations will correspondingly modify and affect the catalytic oxidation.

Any benzene which passes through unchanged can be recovered and returned to the process. The products of the reaction can be recovered and separated from each other in any suit-able manner, for example, by fractional distillation, fractional condensation, crystallization, extraction or otherwise.

The formation of maleic acid, in the manner above described, involves the breaking of the benzene ring or nucleus in a characteristic manner, that is, the breaking of this nucleus or ring in such a way that there remain four carbon atoms united to each other in the form of the stright chain or oxid may possibly be explained by assuming that the remaining two carbon atoms are separated from each other and separately oxidized to different degrees of oxidation. The formaldehyde so formed appears to be oxidized for the most part to carbon dioxid and water.

We claim:

1. The herein described process which comprises subjecting benzene to partial oxidation by an oxy 11 containing gas in the presence of-vanadlum oxid as a catalyzer at a temperature between 300 C. and 550 C.

2. Thezherein described process which comprises subjecting benzene to oxidation by an oxygen containing gas at a temperature between 300 C. and 550 C. in the presence of such a catalyzer that a compound containing hydrogen, oxygen and less than six carbon atoms will be formed.

3. The herein described process which comprises oxidizing lbenzene in the vapor phase at a temperature between. 300 C. and 550 C. in the presence of such a catalyzer that an oxidation product containing four carbon atoms is formed.

4. The method of partially oxidizing benzene, which comprises treating it with an oxygen containing gas at a temperature between 300 C. and 550 C. in the presence of such a catalyst as is ca able of effecting a splittin of the benzene ring with the consequent ormation of an aliphatic carboxylic compound and recovering said compound from the products of reaction.

5. The method of partially oxidizing benzene, which comprises treating it in the vapor phase with an oxygen containing gas at a temperature between 300 C. and 550 C. in the presence of such a catalyst as is capable of efl'ecting a splitting of the benzene ring with the consequent formation of maleic acid.

6. The herein described process which We have comprises oxidizing benzene in the vapor phase at a temperature between 300 C. and 550 C. in the presence of such a catalyzer that part of the carbon atoms are removed from the benzene ring' and a compound is formed containing the other carbon atoms, hydro en and oxygen.

7. file method of partially oxidizing benzene, which comprises treating it in the vapor phase with an oxygen containing gas atsuch a temperature and in the presence of such a catalyst as are capable of effecting a splittin of the benzene ring with the consequent orm'ation of maleic acid, and recovering maleic acid from the products of the reaction.

8. The method of partially oxidizing benzene which comprises treating it in the vapor phase with an oxygen containing gas in the presence of such a catalyst at a temperature between 300 C. and 550 C. that maleic acid and other products will be formed and recovering maleic acid from the other products.

9. The method of partially oxidizing benzene, which comprises treating it in the vapor phase with an oxygen containing gas in the presence of vanadium oxid as a catalyst at a temperature between 300 C. and 550 C. whereby maleic acid and other products are formed, and recovering the maleic acid from the other products.

10. The method of partially oxidizing benzene, which comprises treating it in the vapor phase with an oxygen containing gas at such a temperature and in the presence of such a catalyst as are capable of efl'ecting a splitting of the benzene ring with the consequent formation of maleic acid, recovering the maleic acid from the products of the reaction, and subjecting the residue to a similar oxidizing treatment.

11. The method of partially oxidizing benzene, which comprises treating it in the vapor phase .with an oxygen containing gas at such a temperature in the presence of vanadium oxid that a splitting of the benzene ring with the consequent formation of maleic acid is effected, recovering the maleic acid from the products of the reaction, and subjecting the residue to a similar oxidizing treatment;

In testimony whereof we afiix our signatures.

JOHN M. WEISS. CHARLES R. DOWNS. 

